The present invention is related to a heating, ventilating and air conditioning (HVAC) system. More particularly, the present invention relates to a device to position and contain a sensing element into an enclosure, such as an air duct or a variable air volume (VAV) box, of an HVAC system for detecting air temperature, static pressure, humidity, smoke, impurities, and sampling gaseous mixtures. The present invention further relates to a sensor well device that is inexpensive and quick to install in a field environment.
HVAC systems are designed and installed to maintain environmental conditions within buildings for the comfort of the occupants. A typical building HVAC system is divided into zones and is adapted to maintain each zone within predefined environmental parameters such as humidity and temperature. An air handling unit supplies conditioned air to ductwork that distributes the air to each of the zones. The air handling unit generally includes elements for introducing outdoor air into the system and for exhausting air from the system. Air handlers typically comprise a centrifugal blower that moves air over an evaporator or water coil and pressurizes the air for distribution through a duct at a desired flow rate.
Air flow from an air handling unit to different regions of the zone is regulated by a separate VAV terminal unit, also called a VAV box. The typical VAV box has a damper driven by an actuator to vary the flow of air from the air distribution duct into the associated zone region. VAV boxes serving zones on exterior walls typically have a heating element to increase the temperature of the air that flows in to the associated room. These components are operated by a controller in response to signals from devices that sense air temperature and flow rate. Such a system is shown for example in U.S. Pat. No. 6,338,437, which is incorporated by reference herein.
In the temperature control industry, air sensors are commonly used to as inputs to a building automation control system to maintain temperature, humidity, and static pressure in the controlled environment of a building. During installation of a typical building automation system in a moderate sized building there are hundreds of duct-mounted sensors to install. A common application of duct-mounted sensors is called VAV box discharge temperatures sensors, which measure the air temperature of the discharge (supply air) of an individual VAV box.
Advances in automated testing tools have resulted with an increased need to measure individual VAV box discharge air temperature. Computerized automated testing of VAV box performance is aided by equipping each VAV box with a individual discharge air temperature sensor. Automated testing facilitates testing of multiple VAV box performance in one testing session. This testing application requires either a discharge air temperature sensor or a functional room temperature sensor for each zone controlled by a VAV box.
Often a jobsite construction schedule is rushed and VAV box testing is scheduled to begin without the room temperature sensor points installed or functional. Thus creating a need for an inexpensive and quick installing self-drilling sensor well used for temperature sensing in a VAV box discharge duct.
Known duct temperature element mounting assemblies include Siemens Building Technologies PN 536-811, manufactured in Buffalo Grove, Ill. and others, require an installer to drill three accurate location holes, endure two drill bit changes, install two mounting screws, two wire extenders, four electrical terminations and two wire connecters for installation. The estimated time for installation of the Siemens device is twenty-one minutes. This translates into an expensive installation that may not be economically justified for the project.
FIG. 1 shows a conventional duct mounted temperature sensor 1 mounted in an air duct 2. The sensing element is extended into the duct air stream 3 to measure the air temperature. The mounting bracket 4 through which the sensor 1 extends requires three mounting holes 5, 6 and 7 for installation. The elastic gasket material 8 seals the mounting bracket 4 to the air duct 2 and prevents air leakage. The sensor electrical leads 9, 10 extend approximately five inches and would require a field installed wire extension to connect to a terminal box controller device to sense the air temperature. With this type of duct mounted temperature sensor device the cost and the labor to install it is considerably high. These costs may preclude the installation of this device in the field and automated testing of individual VAV box performance would be degraded.
Therefore, one object of the present invention is to provide a self-drilling sensor well that does not require a separately drilled mounting hole for installation. This is well suited for VAV box and air duct sensor applications as the speed of installation is increased. Still another object of the present invention is to provide a sensor well that enables the sensor element to be removed and replaced quickly for maintenance and repair.
To achieve these objectives, the present invention is a sensor well for use with VAV boxes, air ducts or any enclosure where atmosphere testing is required, wherein the sensor well may itself be used to drill a mounting hole and to be screwed into place. After the sensor well is drilled into place, a sensing element may be hand inserted into a bore within the sensor well until the sensor is seated. Alternatively, the sensor may be integrally provided with the sensor well before the sensor well is drilled into place. An elastic gasket material may be provided to seal the duct opening and prevent the sensor well from vibrating loose. The sensing element is exposed to the atmosphere by one or more cut away slots in the sensor well and by the conduction of the sensor well itself to equalize with the ambient temperature of the atmosphere in the air duct. Accordingly, the sensor well is responsive to changes in atmospheric conditions in the duct environment and can be removed and maintained or replaced with ease. This invention reduces the estimated time it takes to install a sensor in a typical duct and thus reducing the material costs and the labor costs of installation.